The IKEA TRÅDFRI range is excellent. While their smart plugs didn't launch with HomeKit compatibility, it was something they promised and ultimately delivered. They're also pretty cheap too, at £12 in the UK. They're not the smallest of gear, but they've been super reliable (not dropping out) and they respond really quickly. One thing to note, you'll need a driver and bridge to run them, but once you have one of each, it's easy to add more to them. Their bulbs are great too, I've replaced all of my lamp bulbs with IKEA ones.